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This work developed a numeric-based kinematic approach for evaluating the required strength of three-dimensional (3D) geosynthetic-reinforced soil structures (GRSSs) with different water levels. Instead of directly employing the pore-water pressure coefficient r u , this work utilizes numerical simulations to obtain the distribution of pore-water pressures. The presented method avoids to determine the value of r u , which is uncertain as the variation of water tables. A 3D horn-like failure mechanism is discretized to describe the collapse of GRSSs. On this basis, the seepage forces acting on each element of the discretized mechanism are determined by using an interpolation technique. Thanks to the principle of work rate balance, the required reinforcement of geosynthetics is determined through optimization. Sets of design charts are provided for simplicity of practical use, followed by a sensitivity analysis. Results of this paper indicate that the presence of a seepage flow increases the required strength of reinforcements, whereas the inclusion of 3D effects has an opposite effect. The variation of water levels significantly impacts the required strength and the failure pattern of GRSSs. The proposed method in this paper can provide an insight into the design of GRSSs subjected to seepage forces. • A numeric-based kinematic method is developed to evaluate the required geosynthetic strength for 3D GRSSs. • This work utilizes numerical simulations to obtain the distribution of pore-water pressure. • The presence of seepage forces significantly increases the required geosynthetic strength. [ABSTRACT FROM AUTHOR]

Fluid–structure interaction (FSI) problems with large fluid deformations can be a great challenge for numerical simulations using conventional methods. In this paper, we propose a novel hybrid approach of an improved S moothed P article hydrodynamics and smoothed finite E lement M ethod (SPEM) for modeling FSI problems. In SPEM, the edge-based smoothed finite element method (S-FEM) is developed in Lagrangian frame and is used for the first time to model both elastic structures and incompressible flows. For fluid regions with large deformations, the associated finite elements are adaptively converted into particles and the corresponding regions are subsequently modeled using the decoupled finite particle method (DFPM), which is an improved smoothed particle hydrodynamics (SPH) method suitable for modeling incompressible flows with free surfaces. A ghost particle-based interface algorithm to couple existing S-FEM elements and DFPM particles is developed in SPEM to implement the modeling of FSI problems. As the smoothed FEM and decoupled FPM are enhanced FEM and SPH respectively and DFPM is only used for local fluid regions with large deformations, it is expected that SPEM is more accurate and more efficient than the existing coupling approaches of conventional FEM and SPH. Five numerical examples are tested using the proposed SPEM and the comparative studies with results from other sources reveal that SPEM is an effective approach for modeling FSI problems with large fluid deformations. • A smoothed particle element method (SPEM) is developed for modeling fluid–structure interactions. • The Lagrangian smoothed FEM (S-FEM) is used for modeling both structures and fluids. • The decoupled finite particle method (DFPM) is employed to model fluid regions with large deformations. • A ghost particle-based interface algorithm is developed to couple S-FEM and DFPM. • SPEM is more accurate and efficient than existing FEM-SPH or pure SPH approaches. [ABSTRACT FROM AUTHOR]

Detailed structural and chemical analyses reveal that Ti-Si-N coatings prepared with high nitrogen partial pressure and temperature are composed of nm-sized (nearly equiaxed) TiN crystallites encapsulated by ~1.0 nm thin Si-rich tissue phase. This nanocomposite structure allows for superior hardness (37.6 ± 1.5 GPa) and fracture toughness (4.5 ± 0.6 MPa√m). Contrary, deposition at lower nitrogen partial pressure and temperature does not allow for such a clear Si segregation during film growth, leading to nm-sized solid solution Ti 1-x Si x N crystallites. Although having the same Si content of 8.5 at.%, their hardness (32.1 ± 0.9 GPa) as well as fracture toughness (3.0 ± 0.2 MPa√m) is significantly lower. Unlabelled Image [ABSTRACT FROM AUTHOR]

Most of the current studies concerning slope stability assume a toe failure mechanism, which fails to capture the full complexity of slope collapse. In this study, a more comprehensive approach is developed for analyzing seismic slope stability by defining an instability behavior coefficient that considers different failure patterns, including toe, face, and base failure. The proposed coefficient is integrated with a kinematic method of limit analysis to establish a three-dimensional (3D) collapse mechanism that can describe all possible instability behaviors. The impact of earthquake forces on instability behaviors and slope stability is assessed in a modified pseudodynamic manner, which is capable of accounting for the spatiotemporal feature of seismic acceleration. A horizontal slice method is executed for calculating earthquake-induced work rates, as well as a double integral technique to compute dissipation rates due to soil resistance along the sliding surface and work rates generated by soil weight. By applying the principle of energy conservation, the lower-bound solutions of stability numbers are derived, and a further critical solution can be obtained by the combination of the Marine Predators Algorithm and the Nelder-Mead Simplex Algorithm. The proposed method is confirmed to be accurate and effective through comparisons with previous solutions. In addition, a parametric study reveals the effect of the dynamic characteristics of seismic waves on slope stability and instability behaviors. The general approach developed in this study offers a more comprehensive and accurate way to assess seismic slope stability. [ABSTRACT FROM AUTHOR]

Highlights • The finite particle method (FPM) is integrated with particle shifting technique (PST). • FPM-PST shows better performance in accuracy and stability than conventional SPH. • FPM-PST is effective in modeling particulate flows with thermal convection. • Thermal convection has significantly different effects on the motion of hotter and colder particles in the fluid. Abstract Particulate flows with thermal convection are very challenging to simulate numerically due to the existence of constantly moving boundaries and complex heat-fluid coupling effects. Meshfree and particle methods have special advantages in modeling complex fluid flows with moving boundaries. However, previous works based on meshfree modeling mainly focused on either particulate flows only with momentum exchange or natural thermal convection. In this paper, a finite particle method integrated with particle shifting technique (FPM-PST) is developed for modeling particulate flows with thermal convection. FPM is an improved smoothed particle hydrodynamics (SPH) method with better accuracy while extremely irregular particle distribution may lead to ill-conditioned corrective matrix and terminate the simulation. PST can achieve regular particle distribution through shifting highly disordered particles while current PST is based on conventional SPH of poor accuracy. A number of numerical examples demonstrated that FPM-PST is a novel approach for modeling thermal particulate flows with good performance in accuracy and stability. It has better accuracy than the conventional SPH and can obtain comparable results with those from other sources. The unphysical voids can also be avoided by FPM-PST. From the FPM-PST simulations, it is observed that at relatively low Reynolds numbers thermal convection between hotter or colder particles and the fluid causes significant increase or decrease in the drag force acting on particles, while the thermal convection has little influence on the particle motion at relatively high Reynolds numbers. [ABSTRACT FROM AUTHOR]

Smoothed particle hydrodynamics (SPH) is a meshfree Lagrangian particle method, and it has been applied to different areas in engineering and sciences. One concern of the conventional SPH is its low accuracy due to particle inconsistency, which hinders the further methodology development. The finite particle method (FPM) restores the particle consistency in the conventional SPH and thus significantly improves the computational accuracy. However, as pointwise corrective matrix inversion is necessary, FPM may encounter instability problems for highly disordered particle distribution. In this paper, through Taylor series analyses with integration approximation and assuming diagonal dominance of the resultant corrective matrix, a new meshfree particle approximation method, decoupled FPM (DFPM), is developed. DFPM is a corrective SPH method, and is flexible, cost-effective and easy in coding with better computational accuracy. It is very attractive for modeling problems with extremely disordered particle distribution as no matrix inversion is required. One- and two-dimensional numerical tests with different kernel functions, smoothing lengths and particle distributions are conducted. It is demonstrated that DFPM has much better accuracy than conventional SPH, while particle distribution and the selection of smoothing function and smoothing length have little influence on DFPM simulation results. DFPM is further applied to model incompressible flows including Poiseuille flow, Couette flow, shear cavity and liquid sloshing. It is shown that DFPM is as accurate as FPM while as flexible as SPH, and it is very attractive in modeling incompressible flows with possible free surfaces. [ABSTRACT FROM AUTHOR]

Local instability of a compound slope is commonplace in practice. Extant analytical solutions only considered the single global failure pattern, which results in an inaccurate assessment of slope stability. This paper develops a unified analytical framework to account for the local and global instability of a compound slope. A failure pattern coefficient is proposed for the determination of instability behaviors. On this basis, the kinematically admissible three-dimensional (3D) failure mechanism is modified to describe the collapse of slopes. Under the framework of the upper-bound theorem of limit analysis, the external work rates and the internal dissipation rates can be calculated from the unified failure mechanism. The strength reduction technique is introduced into the work rate balance equation, and then the explicit solution of the safety factor is derived. The critical safety factor and slip surface are obtained through a hybrid optimization of the objective function. By way of example, the present solutions are compared with previous solutions and the results of the finite element method. Good agreements of the safety factor and slip surface show the good capability of this study to implement the stability analysis of compound slopes. A detailed parametric study is carried out to reveal the influence of slope geometry, soil strength, and external excitation on slope stability and failure pattern. The method presented in this paper provides a more rigorous solution for the stability assessment of compound slopes. [ABSTRACT FROM AUTHOR]

A need exists for the large-area superconducting YBa 2 Cu 3 O 7-x (YBCO) films with high critical current density for microwave communication and/or electric power applications. Trifluoroacetic metalorganic (TFA-MOD) method is a promising low cost technique for large-scale production of YBCO films, because it does not need high vacuum device and is easily applicable to substrates of various shape and size. In this paper, double-sided YBCO films with maximum 2 in diameter were prepared on LaAlO 3 substrates by TFA-MOD method. Inductive critical current densitiy J c , microwave surface resistance R s , as well as the microstructure were characterized. A newly homemade furnace system was used to epitaxially grown YBCO films, which can improve the uniformity of YBCO film significantly by gas supply and temperature distribution proper design. Results showed that the large area YBCO films were very uniform in microstructure and thickness distribution, an average inductive J c in excess of 6 MA/cm 2 with uniform distribution, and low R s (10 GHz) below 0.3 mΩ at 77 K were obtained. Andthe film filter may be prepared to work at temperatures lower than 74 K. These results are very close to the highest value of YBCO films made by conventional vacuum method, so we show a very promising route for large-scale production of high quality large-area YBCO superconducting films at a lower cost. [ABSTRACT FROM AUTHOR]

We present CCD photometry and low-resolution spectra of the eclipsing binary GR Boo. A new ephemeris is determined based on all the available times of the minimum light. The period analysis reveals that the orbital period is decreasing with a rate of d P / d t = − 2.05 × 10 − 10 d y r − 1 . A photometric analysis for the obtained light curves is performed with the Wilson–Devinney Differential Correction program for the first time. The photometric solutions confirm the W UMa-type nature of the binary system. The mass ratio turns out to be q = 0.985 ± 0.001 . The evolutionary status and physical nature of the binary system are briefly discussed. [ABSTRACT FROM AUTHOR]

Magnetocaloric materials can be useful in magnetic refrigeration applications, but to be practical the magneto-refrigerant needs to have a very large magnetocaloric effect (MCE) near room temperature for modest applied fields (<2 T) with small hysteresis and magnetostriction, and should have a complete magnetic transition, and environmentally friendly. One system that may fulfill these requirements is Mn 2- x Fe x P 1- y Ge y , where a combined first-order structural and magnetic transition occurs between the high temperature paramagnetic and low temperature ferromagnetic phase. We have used neutron diffraction, differential scanning calorimetry, and magnetization measurements to study the effects of Mn and Ge location in the structure on the ordered magnetic moment, MCE, and hysteresis for a series of compositions of the system near optimal doping. The diffraction results indicate that the Mn ions located on the 3 f site enhance the desirable properties, while those located on the 3 g sites are detrimental. The phase fraction that transforms, hysteresis of the transition, and entropy change can be affected greatly by both the compositional homogeneity and the particle size, and an annealing procedure has been developed that substantially improves the performance of all three properties of the material. We also establish a correlation between applied magnetic field to complete the transition and the temperature range of coexistence of the PM and FM phase. On the basis of these results we have identified a pathway to understand the nature and to optimize the MCE properties of this system for magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]

Efficient modeling of rarefied flow has drawn widespread interest for practical engineering applications. In the present work, we proposed the Grad's distribution function for 13 moments-based moment gas kinetic solver (G13-MGKS) and the macroscopic governing equations are derived based on the moment integral of the discrete Boltzmann equation under the finite volume framework. Numerical fluxes at the cell interface related to the macroscopic variables, stress and heat flux can be reconstructed from the Boltzmann equation along the characteristic line directly. The initial distribution function is approximated by Grad's distribution function for 13 moments at the cell interface, so the explicit expression of numerical fluxes could be derived to release the present solver from the discretization and numerical integration in the molecular velocity space. The G13-MGKS with the discrete and explicit form of numerical fluxes are examined by several tests covering the steady and unsteady flows from the continuum regime to rarefied flow regimes. Numerical results indicate that the G13-MGKS could simulate continuum flows accurately and present reasonable predictions for rarefied flows at moderate Knudsen numbers. Moreover, the consumption of computations and memory demonstrates that the present framework could preserve high efficiency. [ABSTRACT FROM AUTHOR]

The degradation of protective hard coatings has a detrimental influence on the performance of metalworking tools like universal drills. Not only do the chemistry and structure of the coating have an influence on the tool damage behavior, but also the tool production steps can cause coating/substrate interface artifacts which weaken the adhesion of the coating to the tool surface. As the current paper will show, the given cutting edge geometry of a drilling tool made of high-speed steel (HSS) caused diminished visibility of the rake face and is referred to as shading. The shading of the rake face caused numerous artifacts, which negatively affected the wear behavior of the tool and the titanium nitride (TiN) coating. Examples of artifacts were (i) different surface roughness for flank and rake face, (ii) burr formation on the rake face, (iii) decreasing coating thickness from flank to rake face, and (iv) a redeposition layer of sputtered material on the rake face. This paper is focused on the failure behavior of a redeposition layer. The layer's occurrence was caused by the redeposition of sputtered substrate material during the sputter cleaning with Ti+ ions and was mainly limited to the area near the cutting edge. An additional local influence through the given rake surface waviness was present. The redeposition layer was an indication of an insufficient sputter cleaning process, whereby chromium oxides remained on the matrix surface. As a result, the layer adhesion of the given TiN/HSS system was lowered significantly, and delamination occurred at the rake face near the cutting edge. This led to increased overall wear velocity and diminished tool lifetime. • Process artifacts: decreasing coating thickness, deformed burr and redeposition layer • Nanocrystalline redeposition layer consisted of Ti and sputtered HSS material. • Redeposition layer thickness was dependent of rake face distance and roughness. • Cracks propagated along HSS/redeposition layer interface. [ABSTRACT FROM AUTHOR]

To investigate the impact of cerebral reperfusion on cardiac contractile function after normothermic regional perfusion (NRP) after anoxic circulatory death in a porcine model. The animals were anaesthetized and biventricular pressure-volume catheters and a pulmonary artery catheter were inserted percutaneously. Through a midline sternotomy, the heparinised animals were cannulated for extracorporeal circulation. Baseline data were obtained before cessation of mechanical ventilation. Death was determined 5 minutes after mechanical asystole and after additional 3 minutes of warm ischemia NRP was started using a heart-lung machine. The animals were randomized before reperfusion to either clamping (CL) (n=8) or non-clamping (NCL) (n=8) of the aortic arch vessels; the infrarenal aorta was clamped in both groups. The NRP-protocol includes early volume loading of the right ventricle, infusion of dobutamine and norepinephrine and gradual wean over 30 minutes. The animals were observed for 180 minutes after weaning from NRP. All animals were successfully weaned from NRP. Both groups demonstrated an acceptable cardiac function after weaning with a mean arterial blood pressure above 75 mmHg and low filling pressures. The NCL group received significantly more norepinephrine (p=0.0484) than the CL group. The left ventricle End-systolic pressure-volume relationship as an index of contractility showed improvement in both groups after wean from NRP compared to baseline (p=0.0009). In the CL group, LV contractility showed a tendency to a better improvement compared to the NCL group (p=0.226) (Fig. 1). The RV showed preserved contractility in both groups. LV contractility but not RV contractility improves after circulatory death and weaning from NRP. The improvement of the left ventricular contractility tends to be better when the aortic arch vessels are clamped compared to upper-body perfusion. [ABSTRACT FROM AUTHOR]

• A unified CFD-particle method is proposed for multiscale rarefied flows. • By introducing the simplified hydrodynamic-wave flux, the particle solver can transfer to the CFD solver adaptively. • Error analysis proves that the simplified treatment preserves the second-order accuracy of the present method. • Tens of times speedup ratio could be achieved compared to the DVM. Coupling the Computational Fluid Dynamics (CFD) with the stochastic particle method to address multi-scale rarefied flows remains of great interest to many researchers. Rather than involving the field decomposition and the information exchange, the simplified hydrodynamic-wave particle method (SHWPM) has been proposed in this paper to automatically switch from the stochastic particle solver to the conventional CFD method in the multi-scale simulation. The weights to couple the respective numerical fluxes are derived based on the integral solution of the Boltzmann equation. By introducing the simplified hydrodynamic-wave flux that can be computed by the linear combination of inviscid and viscous fluxes from the conventional CFD solver, the collision effects of particles are calculated in a macroscopic approach and the number of sampling particles could be significantly reduced in the near-continuum regime. Error analysis demonstrates that the simplified treatment can preserve the second-order accuracy and asymptotic preserving property of the present method in both the continuum and free molecular limits. Several numerical cases over a wide range of Knudsen and Mach numbers exhibit the capability of SHWPM for modeling the multiscale flow accurately and efficiently. The example of hypersonic flow passing a cylinder shows that the SHWPM could achieve tens of times speedup ratio compared to the discrete velocity method (DVM) in the continuum regime. [ABSTRACT FROM AUTHOR]

Abstract: Long term changes in polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) concentrations in soil from four transects across Scotland were measured in three surveys conducted between 1990 and 2007–9. Overall PCB level declined during this period (22.5 to 4.55ng/g, p <0.001) but PBDEs increased (0.68 to 2.55ng/g, p <0.001), reflecting the ban on PCB use in the 1980s while PBDE use increased until about 2004 when the use of penta-mix congener ceased in Europe. The proportion of lighter PCB congeners (28+52) present declined (p <0.001) primarily between 1990 and 1999. However, the proportion of lighter PBDE congeners (47+99) in the soil samples increased (p <0.01) from 1990 to 1999 and declined (p <0.001) thereafter, probably reflecting the introduction of legislation banning penta-BDE products and the degradation of lighter congeners and their translocation. PCBs were slightly higher in two southernmost transects but PBDE concentrations were significantly higher (p <0.001) in the two southern transects than in the two northern transects. This may reflect proximity to areas of high population and industrial activity. It is concluded that temporal and spatial changes in the distribution of PCBs and PBDEs reflect geography, physical processes and legislation. [Copyright &y& Elsevier]

Abstract: A composite of SrTiO3/TiO2 was successfully prepared using TiO2 (Degussa P25) and SrTiO3 powders as starting materials. The composite was characterized by X-ray diffraction (XRD), UV–vis absorption spectrum, scanning electron microscope (SEM), and surface photovoltage spectroscopy (SPS). The SrTiO3/TiO2 composite presents an enhanced photovoltaic response compared with pure TiO2 and SrTiO3. The enhancement was explained by investigating the energy levels of TiO2 and SrTiO3, and the photoluminescence (PL) spectra of TiO2, SrTiO3 and SrTiO3/TiO2. The analysis of energy levels shows that those of TiO2 and SrTiO3 are matching, which improves the separation efficiency of photogenerated carriers. The PL spectra indicate that the formation of SrTiO3/TiO2 composite decreases the recombination rate of photogenerated carriers. Thus the photovoltaic response enhancement is mainly resulting from the improved separation efficiency and decreased recombination rate of photogenerated carriers for SrTiO3/TiO2 composite. [Copyright &y& Elsevier]

Abstract: This paper theoretically proposed a series of formulae for a novel tensile testing method to extract the residual stress in the surface film on metallic substrates. Finite element calculations were conducted to verify the accuracy and reliability of the proposed formulae. From the tensile stress–strain curves of metallic substrates with and without a surface film, one can evaluate the residual stress in the film using these formulae. A tarnish film on a brass substrate formed after immersion in Mattsson’s solution was tested to demonstrate these methods, and the obtained residual stress showed a low difference below 6.8%. [Copyright &y& Elsevier]

Abstract: In this study the effect of micro-voids on the superelastic–plastic behavior of shape memory alloys is investigated. A new constitutive model for porous shape memory alloys, based on the Gurson–Tvergaard–Needleman formulation, is proposed. The model is able to reproduce both forward and reverse stress induced phase transformation, as well as plastic deformation. In addition, the model accounts for the presence of micro-voids and void-growth through a void volume fraction. A one dimensional implementation has been conducted, and results from the new constitutive model is compared with finite element unit-cell analyses. The model does well in reproducing results from unit-cells with void volume fractions . However, some discrepancy is found for void volume fractions that can be attributed to the highly inhomogeneous stress field in the unit-cells which the new model does not account for. The main results show that even for relatively small micro-voids the stress at which transformation and plastic yielding is initiated is lowered. Also, the presence of micro-voids leads to a narrowing of the stress–strain hysteresis which affects the amount of energy dissipated during a superelastic cycle. [Copyright &y& Elsevier]

Abstract: In this work fractography has been used to characterize the fracture surfaces of superelastic, notched round-bar NiTi-specimens. Several fractography studies have been performed for conventional materials, but only few studies have been conducted on NiTi-alloys. The aim of this work is to investigate the effect of semi-circular notches on the fracture behavior of NiTi. The main results indicate that the fracture process is a mixture of cleavage and micro-void coalescence, and that decreasing the notch-radius leads to a loss of ductility which manifests in a reduced fracture strain. Within the range of notches studied in this work, we can observe a transition from high scatter to low scatter in the fracture strain when reducing the notch-radius. By combining fractography studies, finite element analyses and the Rice–Tracey void-growth model, it is argued that fracture is most likely initiated close to the notch for all notch-radii studied herein, and that cleavage or quasi cleavage is the dominating fracture mechanism. [Copyright &y& Elsevier]

Abstract: A TiO2-based composite, ZnFe2O4/TiO2, was prepared with a commercial TiO2 (Degussa P25) and ZnFe2O4 nanopowders using a simple method. The composite was characterized by X-ray diffraction (XRD), UV–vis absorption spectrum, surface photovoltage spectroscopy (SPS) and SEM. The composite presents an enhanced photovoltaic effect compared with the pure TiO2. The trap distributions of TiO2 and ZnFe2O4/TiO2 composite were investigated and the energy levels of TiO2 and ZnFe2O4 were analyzed. The results indicate that the enhancement of photovoltaic effect is mainly due to the increase of photo-generated carrier concentration and improvement of the separation efficiency of photo-generated carriers by the addition of ZnFe2O4. [Copyright &y& Elsevier]

Abstract: Specimens with a rectangular cross-section are commonly used to measure the tensile properties of materials. However, the specimen size may influence the results. In this study, the tensile properties of FH550 and X80 steels were investigated using rectangular cross-section specimens with different thicknesses and the same width. Both an experimental study and a 3D finite element method (FEM) study have been conducted. The results show that the uniform elongation is independent of specimen size, but the post-necking elongation increases dramatically as specimen thickness increases, which was attributed to the stress distribution near neck region. Single factor analysis results show that both the yield and the ultimate tensile strength of the specimens are independent of the thickness when the specimen thickness is larger than 1mm. [Copyright &y& Elsevier]

Abstract: An experimental study with total 504 specimens has been carried out to investigate the fracture and physical properties of the carbon anode materials. The specimens were sampled from anodes produced with machined stub holes. From normal-and Weibull analysis the fracture toughness and the tensile strength showed a clear temperature dependency and orthotropic behavior. It has been found that both the fracture toughness and tensile strength increases with the temperature and are larger for the specimens directed in the horizontal direction than in the vertical direction. The variation in the tensile strength within an anode decreased with the temperature but the variation in the fracture strain increased. The tensile strain appears to be only dependent on the temperature and insensitive to the routine anode properties of the anode material. A multivariate linear regression analyses of the fracture toughness and tensile strength has been conducted and a typical correlation of R 2 =0.5 (R is the Coefficient of Determination) to the measured routine anode properties was found. The thermal expansion coefficient is also larger in the vertical anode direction which makes the crack initiation more sensitive to temperatures. The orthotropic studies also showed that the air permeability has a tendency to be larger in the horizontal direction in the upper part of the anode which can induce unnecessary burning from the anode sides. The influence of the processing parameters in the paste plant and baking furnace has not been presented in this paper. [Copyright &y& Elsevier]

Abstract: An asperity profile function has been proposed that describes the isotropic rough surface of a material. The function is parameterized with three new roughness parameters that control the root mean square height, the slope and the curvature of the rough surface, respectively. Unlike the roughness parameters used in the well known Greenwood–Williamson model, the three parameters introduced in this paper are independent of each other, which is an advantage as this facilitates the characterization of the isotropic random surface of the material. However, a disadvantage with this parameterization is that the roughness parameters are not linked to a contact area equation any more, like the Hertz equations that express contact with linear materials. Different asperity profiles defined by the new roughness parameters were analyzed by a 2D axial symmetric FE-model. The numerical results suggest a procedure for developing a contact area function that are parameterized with the three new roughness parameters, which is also suitable for nonlinear brittle materials. [Copyright &y& Elsevier]

Abstract: In this paper, a relatively new semi-analytical method, called differential transformation method (DTM), is generalized to analyze the free vibration problem of pipes conveying fluid with several typical boundary conditions. The natural frequencies and critical flow velocities are obtained using DTM. The results are compared with those predicted by the differential quadrature method (DQM) and with other results reported in the literature. It is demonstrated that the DTM has high precision and computational efficiency in the vibration analysis of pipes conveying fluid. [Copyright &y& Elsevier]

Abstract: Epitaxial Cu(001) layers were deposited on MgO(001) substrates by magnetron sputtering and the atomic structure of the Cu–MgO interface was characterized by spherical aberration (C S )-corrected high-resolution transmission electron microscopy (HRTEM). The interface structure and the misfit dislocation network were determined by imaging in both the <100> and <110> directions. The dislocation network was found to lie along the <100> directions with a Burgers vector of ½ a Cu <100> deduced from HRTEM images and geometrical phase analysis. The dislocations do not fully accommodate the lattice mismatch, yielding residual stress at the interface and an elongation of the Cu lattice along the [001] direction. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that residual stresses influence the ductile fracture behaviour. In this paper, a numerical study was performed to assess the effect of residual stresses on ductile crack growth resistance of a typical pipeline steel. A modified boundary layer model was employed for the analysis under plane strain, Mode I loading condition. The residual stress fields were introduced into the finite element model by the eigenstrain method. A sharp crack was embedded in the center of the weld region. The complete Gurson model has been applied to simulate the ductile fracture by microvoid nucleation, growth and coalescence. Results show that tensile residual stresses can significantly reduce the crack growth resistance when the crack growth is small compared with the length scale of the tensile residual stress field. With the crack growth, the effect of residual stresses on the crack growth resistance tends to diminish. The effect of residual stress on ductile crack growth resistance seems independent of the size of geometrically similar welds. When normalized by the weld zone size, the ductile crack growth resistance collapses into one curve, which can be used to assess the structural integrity and evaluate the effect of residual stresses. It has also been found that the effect of residual stresses on crack growth resistance depends on the initial void volume fraction f 0, hardening exponent n and T-stress. [Copyright &y& Elsevier]

Abstract: A systematic study has been carried out by using 2D axisymmetric models to understand the ductile fracture behavior of pipes with internal and external circumferential cracks. Crack growth resistance curves have been computed using the complete Gurson model. Pipes with various diameter-to-thickness ratios, internal pressure, crack depths and material properties are analyzed. The results have been compared with those of corresponding SENT and standard SENB specimens. It clearly indicates that the SENT specimen is a good representation of circumferentially flawed pipes and an alternative to the conventional standard SENB specimen for the fracture mechanics testing in engineering critical assessment of pipes. [Copyright &y& Elsevier]

Abstract: A strong geometry dependence of ductile crack growth resistance emerges under large scale yielding. The geometry dependence is associated with different levels of crack tip constraint conditions. However, in a recent attempt to identify appropriate fracture mechanics specimens for pipeline steels, an “independent” relationship between the crack growth resistance curves and crack depths for SENT specimens has been observed experimentally. In this paper, we use the complete Gurson model to study the effects of crack depth and specimen size on ductile crack growth behavior. Crack growth resistance curves for plane strain, mode I crack growth under large scale yielding conditions have been computed. SENB and SENT specimens with three different specimen sizes, each specimen size with three different crack depths, have been selected. It has been found that crack tip constraint (Q-parameter) has a weak dependence on the crack depth for specimens in the low constraint regime. [Copyright &y& Elsevier]

Various pharmaceutical residues are being discharged from wastewater treatment works (WTW) effluents, the impact of which on river water quality is of high relevance to environmental risk assessment. The concentrations of eleven pharmaceutical compounds were determined in three WTWs in England, and the river Ouse receiving effluents from Scaynes Hill WTW. Results show that five compounds propranolol, sulfamethoxazole, carbamazepine, indomethacine and diclofenac were detected in all wastewater and river water samples, with carbamazepine showing the highest concentrations (up to 2336ngL¿1) in WTW influent. Different compounds were removed to different extent in the WTWs, varying from 43 to 92%, with the highest performance obtained by the WTW with tertiary treatment (sand filtration). The pharmaceutical residues from Scaynes Hill WTW were eventually discharged into the river Ouse, causing an elevation in their concentrations downstream of the outfall. This was confirmed by the good agreement between measured concentrations and those predicted by a simple dilution model. [Copyright &y& Elsevier]

Abstract: Finite element analyses using COMSOL have been carried out to study the heat transfer behavior and storing capacity of concrete walls with air cavities, and to explore the possibility of using one-layer and two-layer one-dimensional models with equivalent thermal conductivity and mass density to represent the effect of concrete walls with air cavities in a building energy simulation. Three typical wall geometries were chosen and both stationary and transient analyses have been carried out. The stationary analyses were performed first to find the equivalent thermal conductivity which was further used in the transient analyses to fit the equivalent mass density. Because of the presence of air cavities the equivalent thermal conductivities are always smaller than the bulk thermal conductivity. However, for the one-layer model an exaggerated equivalent mass density as high as two times the bulk density should be used in order to simulate the heat storing capacity of the concrete walls with air cavities. The values of the fitted equivalent mass density are strongly dependent on the wall thickness. [Copyright &y& Elsevier]

Abstract: Residual stresses play a crucial role in structural integrity assessment. In this study, a large cracked cylinder with a weld in the center is applied to investigate the effect of residual stresses on the crack-tip constraint. A modified boundary layer model with a remote displacement-controlled elastic K-field and T-stress under small scale yielding has been used to simulate the problem. A two-dimensional tensile residual stress field due to the weld is introduced into the model by the so-called eigenstrain method. It has been shown that the residual stresses can significantly elevate the crack-tip constraint and thus increase the probability for cleavage fracture. The constraint parameter R introduced by the authors can be used to rank the crack-tip constraint induced by the bi-axial residual stresses. The R value decreases with the increase in the applied J-integral. The residual stress-induced constraint is also coupled with the T-stress. The R value becomes smaller with larger T-stress. [Copyright &y& Elsevier]

Abstract: This paper illustrates an efficient contour integral procedure to obtain stress intensity factors in combination of the asymptotic analysis with finite element analysis. Note that this set-up is very general: the material can be anisotropic elastic, and the specimen can be built as a bi-material system, notches of arbitrary opening angle can be analyzed (γ =0→crack, γ =180°→free edge). The purpose of this technical note is to comment on three issues in the notch mechanics: the interpretation of the eigenvalue equation, the definition of stress intensity factors, and the effect of the outer contour location on H-integral evaluations. [Copyright &y& Elsevier]

Abstract: Research into the analysis and monitoring of steroidal estrogens has grown significantly over the last decade, resulting in the emergence of a range of applicable techniques. In this study, three popular techniques, gas chromatography–mass spectrometry (GC–MS), gas chromatography–tandem mass spectrometry (GC–MS–MS) and liquid chromatography–tandem mass spectrometry (LC–MS–MS) for the analysis of three highly potent steroidal estrogens in the aquatic environment have been compared. It has been observed that overall, the three techniques appear comparable in generating similar estrogen concentrations for river and effluent samples. Of the three techniques, the GC–MS technique is the simplest to operate, but fails to detect the estrogens at the lower-end of environmentally relevant concentrations. The tandem MS techniques are more selective than MS, and therefore able to detect lower concentration levels of the three steroidal estrogens of interest. However, the LC–MS–MS technique is more susceptible to matrix interferences for the analysis of samples, resulting in a reduction of the signal-to-noise ratio and a subsequent reduction in reliability and stability compared to GC–MS–MS. With the GC–MS–MS technique offering increased selectivity, the lowest limits of detection, and no false positive identification, it is recommended to be the preferred analytical technique for routine analysis of estrogens in environmental water samples. [Copyright &y& Elsevier]

Abstract: This study focuses on the stress intensity factors for free edges in multi-layered structural components. The effects of elastic constants of various material combinations on the weak singularity at free edges are analyzed. Using the H-integral approach, the effects of elastic mismatch parameters, the bond area and the thickness of the thin metal layer on the stress intensity factor are quantified and the results are compared with detailed finite element solutions. A good agreement between numerical predictions obtained from the H-integral and the detailed FE results is achieved, showing the applicability of this approach. Similar to a crack problem, the singular elastic field dominates in an annular region adjacent to the notch tip. The relationship between the valid range of the K-dominated field and the thin-film thickness is then demonstrated. Furthermore, the competition of crack initiation between the free edge interface (180° opening angle) and a 90° notch interface in a generic specimen is investigated, in order to find out which is the prevailing failure mode. Comparison between isotropic Si and anisotropic Si substrate is also illustrated. Anisotropy of the Si substrate has a significant influence on the stress intensity factor when combined with an Au or Al metal layer but not with a Cu layer. Additionally, standardized numerical formulae of the dimensionless stress intensity factor have been derived to guide the engineering application. [Copyright &y& Elsevier]

Abstract: 4-Dimethylaminoazobenzene (DAB) is anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity in experimental animals. The trace detection of DAB is of great significance in environmental protection and safe life of the people. To test the availability of DAB trace detection using surface-enhanced Raman scattering (SERS), the SERS spectra of DAB single molecules adsorbed on the silver particle aggregates in colloid were investigated. The phenomena of blinking, spectral diffusion, and intensity fluctuations of the vibrational lines in the SERS spectra were observed. Statistical analysis of spectral intensity fluctuations indicates a multimodal distribution of some specific Raman bands, which are consistent with the identification of single molecule detection. Our results demonstrated that SERS can be applied to the trace detection of DAB molecules and other azo dyes. [Copyright &y& Elsevier]

Abstract: During installation and operation, pipeline steels may suffer from plastic pre-deformation (prestrain) due to accidental loading, cold bending or ground movement. The plastic prestrain history not only modifies steels’ yield and flow properties but also influences their fracture performance. This paper focuses on the effect of plastic prestrain history on ductile fracture resistance. Single edge notched tension (SENT) specimens have been selected for the numerical study and the crack is assumed to exist before a prestrain history was applied. The complete Gurson model has been applied to simulate the ductile fracture behaviour. The results show that prestrain history can reduce the fracture resistance significantly and neither the history-independent resistance model nor material-memory resistance model existing in the literature can be used to describe the prestrain history effect. Based on the numerical results an approximate history-dependent resistance model is proposed. The results also suggest that it is important to take the prestrain effect into consideration in future structural integrity assessment procedure for pipelines. [Copyright &y& Elsevier]

Liquid sloshing flows interacting with deformable structures are difficult to be numerically simulated due to the co-existence of moving fluid-structure interfaces and breaking free surfaces. As a Lagrangian and particle-based method, the smoothed particle hydrodynamics (SPH) method has natural advantages in handling free-surface flows. The smoothed finite element method (SFEM) provides a reliable tool to capture the associated structural deformations, and it can solve the "overly-stiff" problem in the conventional FEM. In this work, the coupling strategy of an improved SPH version and SFEM is integrated with advanced fluid modeling techniques, and is extended and validated for modeling liquid sloshing with rigid or deformable structures. Both the rigid wall boundaries and deformable structures are reproduced by the elements, whereas the fluid particles with a different resolution can be adopted. The integrated δ -SPH model can significantly alleviate the spurious high-frequency noise of the computed impact pressure in a sloshing process. The particle shifting technique helps improve both accuracy and robustness of the fluid flow model. The virtual particle coupling strategy is effective to transfer information between SPH particles and SFEM elements. Various numerical tests show that the present coupling approach is very effective for modeling violent sloshing with deformable baffles or deformable container walls. This method is more accurate than the conventional coupling of SPH-FEM and can obtain results very close to the experimental observations compared with some numerical approaches from other sources. [ABSTRACT FROM AUTHOR]

Abstract: This paper studies the effect of welding residual stresses on the near tip stress field in single edge notched bending and tensile specimens. A combined effect of mechanical stresses by the applied load and residual stress on the crack tip constraint is analyzed. Three initial residual stress distributions were considered. It has been shown that the crack tip stress field is strongly influenced by the residual stresses and a new parameter, R, is proposed to characterize the residual stress induced crack tip constraint. The results therefore suggest a three-parameter approach (CTOD, Q and R) to characterize the crack tip stress field in the presence of residual stress where CTOD sets the size scale over which large stresses and large strains develop, and the geometry constraint parameter Q and the new residual stress induced constraint parameter R control the actual crack tip constraint level. For the cases analyzed, R is in general positive, which indicates that residual stress can enhance the crack tip constraint. However, the results also indicate that the R decreases towards zero and the effect of residual stress on crack tip constraint can be neglected when a full plastic condition is approached in the specimen. [Copyright &y& Elsevier]

Abstract: This paper addresses the residual stresses and their effect on microcracking in polycrystalline ceramic materials. Residual stresses at microstructural level in titanium diboride ceramics, as a result of thermal expansion anisotropy, were analyzed by finite element method using Clarke’s model. Damage mechanics based cohesive zone model was applied to study grain boundary microcracking, propagation and arrest. Quantitative relations between temperature variation, grain boundary energy, grain size, final microcrack length as well as microcracking temperature are established. [Copyright &y& Elsevier]

Abstract: A nanoindentation-based flat punch method has been developed to determine the stress–strain behaviour of single micron-sized Ugelstad polystyrene-co-divinylbenzene (PS–DVB) particles in compression. Five groups of particles with identical chemical compositions but different diameters have been tested. The diameter of the PS–DVB particles varied from 2.6μm to 25.1μm. Constant relative deformation rate has been applied with two maximum strain levels of 5% and 10%. Results show that the particle compressive stress–strain behaviour is strongly size-dependent. The smaller the particle size is, the stiffer the particle behaves. Analyses indicate that the pre-load and adhesion during the flat punch test play a minor role on the size effect. The presence of a core–shell structure can possibly be a main contribution to the size effect. Finite element analyses have been carried out to demonstrate this surface shell effect. [Copyright &y& Elsevier]

Abstract: In this study we focus on the fracture behavior of two types silicon-thin film glass-silicon (Si-Glass-Si) triple stacks specimens with a sharp corner. We determine the notch stress intensity factor K n for both specimens using a combination of the Williams eigenfunction expansion method, Stroh’s sextic formalism, finite element analysis, and the path-independent H-integral. Empirical solutions of dimensionless stress intensity factors are proposed for two typical specimens, and the dependence of geometry is analyzed. Furthermore, the effect of glass thickness on stress intensity is explored for anodic-bonded Si-Glass-Si triple stacks. We discuss the feasibility of using a critical value of K n to correlate the failure results for both specimens with various bond area and glass thickness. [Copyright &y& Elsevier]

Abstract: Before and during operation, pipelines may suffer from plastic pre-deformation due to accidental loading, cold bending and ground movement. Plastic prestrain not only modifies steel''s yield and flow properties but also influences its fracture performance. This paper focuses on the effect of prestrain history on crack driving force and crack tip constraint. A single-edge notched tension specimen has been selected for the study and the crack is assumed to exist before a prestrain history was applied. The results show that prestrain history has a strong effect on the crack tip stress field. A new parameter has been proposed to characterize the prestrain-induced crack tip constraint. For the same crack tip opening displacement level, prestrain history will elevate the crack tip stress field. The prestrain-induced constraint decreases with the increase of loading. [Copyright &y& Elsevier]

Abstract: A solid-phase extraction (SPE) followed by liquid chromatography–electrospray ionisation tandem mass spectrometry (LC–ESI-MS–MS) method was developed and validated for simultaneous analysis of 11 pharmaceutical residues (propranolol, sulfamethoxazole, meberverine, thioridazine, carbamazepine, tamoxifen, mecoprop, indomethacine, diclofenac, meclofenamic acid and monensin) in environmental water samples. The collision energy chosen for the multiple reaction monitoring (MRM) experiment was optimised. A number of parameters that may affect the recovery of the pharmaceuticals, such as the type of SPE cartridges, eluents, as well as water properties including pH value, salinity and concentration of colloid and surfactant were investigated. It is shown that the Oasis HLB SPE cartridge produced the best recoveries of the target pharmaceuticals while methanol was efficient in eluting pharmaceuticals from SPE cartridges. The recovery of some target compounds was enhanced with increasing salinity, but reduced by increasing pH value, and unaffected by surfactant concentration (0–10μg/l). The recovery of most compounds was slightly increased by the presence of colloids (0–10mg/l), which however caused a reduction in recovery for sulfamethoxazole and meberverine. The optimised method was further verified by performing spiking experiments in river water and seawater matrices, with good recovery and reproducibility for all except two compounds. The established method was successfully applied to environmental water samples from East Sussex, UK, for the determination of the target pharmaceuticals. [Copyright &y& Elsevier]

Abstract: Micron-sized metal coated polymer particles are used in developing anisotropic conductive adhesives (ACA). The mechanical properties of polymer particles are of crucial importance for the reliability and design of ACA. In this paper we present a method to determine the mechanical properties of polymer sphere particles under large deformation by using a flat punch test-soft elastic sphere against a rigid flat. Finite element analyses have been carried out to study large deformation contacts. It has been shown that the classical Hertz solution works only for very small sphere deformation (less than 1% compression strain) and Tatara’s solution works well for sphere compression up to 20%, beyond that large strain effect should be considered. For compression less than 20%, both the compression stress–strain curves and lateral expansion strain–compression strain curves can be normalized by a function of the Poisson ratio. Based on the finite element results, explicit equations describing these relations are presented for determining the Young’s modulus and Poisson ratio of polymer particles at large deformation. The proposed method has been applied to analyze the experimental results of typical polymer particles used for conductive adhesives from a specially built capacitance-based flat punch test. [Copyright &y& Elsevier]

Abstract: An optimisation of derivatisation methods for the simultaneous determination of endocrine disrupting chemicals (EDCs) in water by solid-phase extraction (SPE) gas chromatography–mass spectrometry (GC–MS) was developed in this study. Seven highly potent EDCs including 17β-estradiol (E2), estrone (E1), 16α-hydroxyestrone, 17α-ethynylestradiol (EE2), bisphenol A, 4-nonylphenol and 4-tert-octylphenol were selected as the target compounds. The SPE technique, followed by the derivatisation with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) was used for the extraction recoveries of compounds from water and effluent samples. The stability of the silylation derivatives under different reaction conditions was investigated. The combined use of BSTFA and pyridine as derivatisation reagents, together with the use of hexane as the final solvent, was preferred in order to generate more stable derivatives of EDCs. The relative response factor (RRF) of all derivatives except that of EE2 was stable 120h after derivatisation. The addition of pyridine as derivatisation reagent with BSTFA can prevent the conversion of EE2 to other products during the reaction. Several parameters that may affect the recovery of EDCs, such as the SPE flow rate, and water properties including aquatic colloid content and surfactant concentration were tested. The results showed that the flow rate (1–25mLmin−1), colloid concentration (0–50mgL−1) and surfactants concentration (0–10μgL−1) did not cause significant decrease in the EDCs recovery. [Copyright &y& Elsevier]

Abstract: Materials constitutive behaviour at high temperature is dependent on both temperature and microstructure. This paper presents a method to retrieve the temperature and microstructure dependent apparent yield strength of 6XXX aluminium alloys from the reaction force–temperature curves measured at the centre of the gauge length of a cylindrical specimen. The specimen is clamped at both ends and subjected to a controlled thermal history via induction heating. The experimental procedure is based on the test setup proposed by Satoh to determine residual stresses in welds. Various effects on the accuracy of the method have been investigated, including the effect of heating rate, hardening and testing frame stiffness. Examples have been shown for the aluminium alloy 6082 in T6 temper condition. [Copyright &y& Elsevier]

Abstract: Protein immobilization is of great importance for the development of biosensors, immunoassays and microfluidic devices. In this work, we study the in situ bio-functionalization and cell adhesion in microfluidic channels. A way of covalently linking antibodies on the channel surface while keeping their bio-functionality and its application for efficient cell adhesion were shown. Soft lithography has been used to fabricate simple microfluidic devices and all chemical and biologic materials were injected into microfluidic channels for the in situ bio-functionalization and cell adhesion. Our results show that the established bio-processing protocol significantly enhances the protein immobilization on both glass and poly-dimethylsiloxane surfaces, thereby allowing one to develop a large number of applications. [Copyright &y& Elsevier]